Characterization of gold/PMMA hybrid nanomaterials synthesized by hard X-ray synchrotron radiation

In this study,new types of hybrid gold poly(methyl methacrylate) (PMMA) nanomaterials are synthesized.Both PMMA spheres coated with gold nanoparticles and gold nanoparticles coated with PMMA can be synthesized using different ratios of HAuCl4 and MMA precursors,by exposing the mixtures to hard X-ray synchrotron radiation without the use of a reducing agent.According to the photochemical mechanism,gold nanoparticles will precipitate from a solution of HAuCl4 on exposure to synchrotron radiation,followed by the synthesis of PMMA by the polymerization of MMA monomers.These reactions can result in the formation of two different types of new hybrid nanomaterials.When a 1:1 volume ratio of HAuCl4 to MMA is used,we obtain PMMA spheres coated with gold nanoparticles.When a 10:1 ratio of HAuCl4 and MMA is used,we obtain gold nanoparticles coated with PMMA.The hybrid gold/PMMA nanostructures are characterized by transmission electron microscopy,elemental analysis,dynamic-light scattering analysis,gel permeation chromatography and Raman spectroscopy.The hybrid nanomateriais have potential application in the fields of biosensors and drug delivery.     

A moiré microscope for finite deformation micro-mechanical studies

A new version of a moiré microscope is presented that embodies the theory of optical moiré interferometry. To interrogate the deformed specimen grating, the device uses a transmission diffraction grating that allows for a simple and quick change of the virtual reference grating vector without disturbing the optical alignment of the other components in the optical train. To analyze deformation from the acquired moiré interference fringe patterns, the displacement light-itensity moiré optical law introduced by Sciammarella is revisited. The analysis of deformation is consistent with the continuum principles of finite deformation and can readily be used to obtain micro-mechanical quantities of interest such as the local strains, stretches and rotations.     

Effective Separation of Human Milk Glycosides using Carbon Dioxide Supercritical Fluid Chromatography

Carbohydrate purification remains problematic due to the intrinsic diversity of structural isomers present in nature. Although liquid chromatography-based techniques are suitable for analyzing or preparing most glycan structures acquired either from natural sources or through chemical or enzymatic synthesis, the separation of regioisomers or linkage isomers with a clear resolution remains challenging. Herein, a carbon dioxide supercritical fluid chromatography (SFC) method was devised to resolve 18 human milk glycosides: oligomers (disaccharides to hexasaccharides), fucosylated regioisomers (lacto-N-fucopentaose I, III, and V; lacto-N-neofucopentaose V; lacto-N-difucohexaose III; blood group H₁ antigen; and TF-LNnT), and connectivity isomers (lacto-N-tetraose/lacto-N-neotetraose and para-lacto-N-hexaose/para-lacto-N-neohexaose/type-1 hexasaccharide). The analysis of these glycosides represents a major limitation associated with conventional carbohydrate analysis. The unprecedented resolution achieved by the SFC method indicates the suitability of this key technology for revealing complex human milk glycomes.     

Magnetic properties of Fe/Pt films by symmetrical insertion of Ag

Ultrathin Ag (0.5 nm) pinning layers (APLs) were symmetrically inserted into [Fe/Pt] bilayers to introduce controllable defects on the interfaces between Ag and Fe/Pt multilayers. The highest coercivity 7700 Oe and remanent squareness 0.95 were obtained with five APLs. The large enhancement in coercivity (75% increment compared with that without APL) is due to the relative uniform defects that introduced pinning effects on the interfaces between the APLs and Fe/Pt multilayers. According to the distribution of angule- dependent coercivity of Fe/Pt multilayers without and with APLs, a tendency is suggested of weakened domain-wall motion while enhanced rotation of reverse domain mode.     

Atomic structures of silicon and metal surfaces; pulsed-laser tof atom-probe and field ion microscopy

The atomic structure of a solid surface can be imaged with the field ion microscope and the chemical species of surface atoms can be identified by the time-of-flight atom-probe. By combining a pulsed-laser technique to field ion microscopy, atomic processes in surface reconstruction and growth of thin films can be studied with a resolution of 2.5 Å, and in time steps of a few nanoseconds. The mass resolution and material applicability of a pulsed-laser time-of-flight atom-probe are greatly improved. Thus materials of poor conductivity such as high purity silicon can be analyzed with excellent mass resolution. It is also ionion energy analyzer with an accuracy and resolution of 2 parts per 100 000 and an ion reaction and dissociation time analyzer of 20 fs time resolution. Some recent studies with these techniques such as (1) surface reconstruction of Pt and Ir(001) and (110) surfaces, (2) observation of well ordered and atomically resolved images of pure silicon surfaces and surface reconstruction of many surfaces of silicon, and (3) formation of multiple charge cluster ions and dissociation of compound ions by atomic tunneling in an electric field etc., will be briefly described. We want to emphasize that recent studies of Si and metal surfaces are concerned with atomic structures of thermally equilibrated surfaces, and not with field evaporated surfaces as in earlier studies.     

Microwave switching behaviors of Fe/Ag/Fe/Ag epitaxial films

In this study, Fe/Ag/Fe/Ag ferromagnetic structures were epitaxially grown on a GaAs(1 0 0) substrate. Using the Network Analyzer (Agilent 8510C), FMR (ferromagnetic resonant) signals were observed in samples as the in-plane magnetic field was applied to either hard- or easy-axes. Of interest was that our sample demonstrated a FMR-switching behavior in hard-axis but not in easy-axis. The detecting data showed that the switch magnetic field was much smaller than what has been stated previously in Fe/Cu/Fe systems by other laboratories. In addition to the frequency switch in FMR, we also observed a magnetic reversal behavior in its M–H curve. Data presented that both of the FMR and magnetic reverse took place in the same direction (hard-axis).     

Ranking fuzzy numbers with integral value

Ranking fuzzy numbers is important in decision making. Since very often the alternatives are evaluated by fuzzy numbers in a vague environment, a comparison between these fuzzy numbers is indeed a comparison between alternatives. This paper proposes a method of ranking fuzzy numbers with integral value. The method, which is independent of the type of membership functions used and the normality of the functions, can rank more than two fuzzy numbers simultaneously. It is relatively simple in computation, especially in ranking triangular and trapezoidal fuzzy numbers. Further, an index of optimism is used to reflect the decision maker's optimistic attitude. Discussion on comparative advantages is included.     

A Newton/upwind method and numerical study of shock wave/boundary layer interactions

The objective of the paper is twofold. First we describe an upwind/central differencing method for solving the steady Navier–Stokes equations. The symmetric line relaxation method is used to solve the resulting algebraic system to achieve high computational efficiency. The grid spacings used in the calculations are determined from the triple-deck theory, in terms of Mach and Reynolds numbers and other flow parameters. Thus the accuracy of the numerical solutions is improved by comparing them with experimental, analytical and other computational results. Secondly we proceed to study numerically the shock wave/boundary layer interactions in detail, with special attention given to the flow separation. The concept of free interaction is confirmed. Although the separated region varies with Mach and Reynolds numbers, we find that the transverse velocity component behind the incident shock, which has not been identified heretofore, is also an important parameter. A small change of this quantity is sufficient to eliminate the flow separation entirely.     

High Energy Fuels I: A Novel Preparation of Exo-Tetrahydrodicyclopentadiene by Isomerization of Endo-Tetrahydrodicyclopentadiene

Endo-tetrahydrodicyclopentadiene (IV) is isomerized in the presence of trifluoromethanesulfonic acid (I) to give exo-tetrahydrodicyclopentadiene (V). At higher acid concentrations, the isomerization occurs instantaneously. The preferred molar ratio of I to IV is in the range 0.05 to 4.0 and the preferred temperature is in the range 20°C to 100°C. Under these conditions, virtually no admantane is formed and undesirable C₁₀H₁₆ isomers can be reduced to a minimum. Besides the homogeneous system, the acid catalyst also works in a two-phase heterogeneous system. The spent acid in the heterogeneous system can be reused without losing catalytic effectiveness.